1. Field of the Invention
This invention relates generally to a cassette tape recording and/or reproducing apparatus, and more particularly is directed to the so-called head base assembly thereof, that is, the structure by which the magnetic head or heads and pinch roller are movably supported in such apparatus.
2. Description of the Prior Art
In cassette tape recording and/or reproducing apparatus, where size is not of critical importance, the head base plate which carries a recording and reproducing head and an erasing head is mounted on the chassis for rectilinear movements between operative and inoperative positions. However, when the size of the apparatus is of critical importance, for example, in the case of cassette tape recording and/or reproducing apparatus which is to be portable on the person of the user, the head base plate is usually pivotally mounted on the chassis for minimizing the space required therefor. For example, as shown in U.S. Pat. No. 4,010,493, one end of the head base plate may be pivotally mounted on a pivot post extending perpendicular from a chassis, and a recording and reproducing head and an erasing head are mounted on the head base plate at positions thereon remote from the pivot post so as to be movable between inoperative and operative positions in response to corresponding pivotal movements of the head base plate.
However, in such prior arrangements employing a pivoted head base plate, the end portion of the head base plate remote from the pivot post is susceptible to undesirable vibration or small movements in the direction normal to the plane of the chassis on which the cassette is located. If such vibrations or small movements occur in the recording or reproducing mode of the apparatus, the recording and reproducing head and the erasing head do not precisely engage the desired track or tracks on the magnetic tape.
In an attempt to avoid the above described undesirable vibrations or small movements of the pivoted head base plate in directions normal to the plane of the chassis, it has been proposed, for example, in U.S. Pat. No. 4,511,941, issued Apr. 16, 1985, and in U.S. Pat. No. 4,453,189, issued June 5, 1984, each having a common assignee herewith, to provide the chassis with stabilizing projections extending under the pivoted head base plate at a distance from the pivot post and being slidably engaged by the head base plate under the urging of a coil spring which extends around the pivot post and acts axially against the head base plate. However, the force of such spring acting on the head base plate at the pivoting axis thereof is insufficient to reliably prevent movements of the head base plate away from the stabilizing projections with the result that vibrations of the head base plate normal to the plane of the chassis can still occur at locations remote from the pivot post.
The above described arrangements pose another serious problem in that the head base plate is usually of one-piece construction and has both a pinch roller and at least one magnetic head mounted thereon at relatively smaller and larger distances, respectively, from the pivot post. In such case, the angular movements of the head base plate between its operative and inoperative positions must be large enough so that, in the inoperative position, the pinch roller will be withdrawn from a tape cassette located on the chassis to permit the loading or ejecting of the tape cassette. Since the magnetic head is at a further distance from the pivot post than the pinch roller on the one-piece head base plate, the angular movement of the head base plate to its inoperative position will result in an undesirably large movement of the magnetic head away from the tape cassette with the result that such arrangement is wasteful of the space required therefor.